Electrical discharge device



Nov. 10, 1931. F. s. MCCULLOUGH ELECTRICAL DISCHARGE DEVICE Filed April 25, 1928 lV/J HTTOE/YEK Patented "N 'vf." 10,-.1931

na'rarrr; OFFICE UNITED STATES 5;" KCCULLOUGH, 01 EDGEWOOD, PENNSYLVANIA mc'rarcu. msommn nmcn.

Application filed April 25, 1928. Serial No. 272,715.

- My invention relates to electrical discharge devices, and particularly to thermionic re- My invention possesses other objects and valuable features, some of which will be set forth in the following description of my 1n-' vention which is illustrated in the drawings forming part of the specification. It is to be understood that I do not limit myself to the showing made by the said description and drawings, as I may adopt varying forms of my invention within the scope of the claims.

A number of thermionic relays have been devised having more than the customary three electrodes, one of these being that described in my co-pending application, Serial Number 123,086, filed July 17, 1926. In most of these devices the additional element takes.

the plate; the second when it is placed between the grid and the cathode. Ordinarily they are not secured simultaneously since the difiiculty in constructing a device of this character increases enormously with each additionalelectrically separate element, and the obvious expedient of adding a third grid to make a five electrode tube has been prohibitively difiicult.

The four electrode tubes have been used in small sizes only. The positively charged shield is subject to severe electronic bombardment, and the heat developed thereby would quickly destroy a tube of this character if it were used to handle large power.

Recent developments in radio communication have emphasized the importance of shortwaves or high frequencies, and an increasing amount of traflic is carried in the communication channels lying between 10 and 100 meters. Grid-to-plate capacity effects render the ordinary three electrode construction almost useless on the shorter of these wave lengths, and there is therefore, an urgent need for tubes embodying the shield principle and capable of handling enough power to assure positive, 24 hour communication through interference. Such a tube is provided by my invention.

Referring to the drawings Figure 1 is an axial vertical sectional view of a preferred embodiment of my invention.

Figure 2 is a transverse sectional View, the plane of section being indicated by the line 22 of Figure 1.

Figure 3 is a detail view showing the method of mounting the grid and filament on the stem of the tube. The direction of the view is indicated by the arrow 30f Figure l.

Figure 4 is a detail view showing the method of sealing the water-cooled shield through the glass vessel.

Figures 5, 6 and 7 are diagrammatic views showing modified arrangements of grid and shield.

Broadly stated, my invention comprises an electrical discharge apparatus having a cathode, an anode, and acontrol electrode or grid. Interposed between adjacent elements of the grid, and extending beyond its envelope, is the fourth electrode or shield, which is preferably a flattened tube opening externally of the evacuated chamber enclosing the electrodes, to permit the circulation of a cooling fluid.

A preferred embodyment of my invention comprises a glass bulb 6 within which is sealed a stem 7. Held by the press 8 of the stem are the filament leads 9, the filament support or dummy 11, the grid lead 12 and the grid dummy 13.

The filament 14 is a U shaped wire having an electron emitting surface, and its apex is supported by a small coiled spring 16 attached to the filament support 11.

The grid comprises a plurality of parallel wires 17 extending between the arms of an upper annular spider 18 and a similar lower spider 19 which is carried by the grid lead 12 and dummy 13.

The grid wires lie between the convolutions of the shield 21. The shield preferably comprises a flattened metal tube, bent back and forth so that the elements of grid and shield are mutually interposed. The transverse dimension of the shield is, of course, greater than that of the grid wires, and the positioning of the parts is such that the shield extends beyond the envelope of the grid. The term envelope is used in its mathematical sense to denote a surface conceived as tangent to the elements of the grid.

The shield opens externally of the bulb, the ends of the tube being brought through the glass as is described in my co-pending application, Serial Number 269,439, filed April 12, 1928. A thin copper sleeve 22 is welded to the unflattened end 23 of shield. The sleeve bridges a portion of the tube, its free end being supported on a collar 24 which serves as an abutment. A getter 26 is placed within the space between the shield and the sleeve, the latter having ports 27 opening within the bulb. The bulb is fused to the sleeve to form a seal 28.

A cylindrical anode or plate 31, having a closed end, surrounds the other electrodes and forms a part of the evacuated vessel within which they function. The open end of the anode is provided with a flange 32 to which is welded an annular member 33 of U shaped cross section, formed preferably of thin copper. The inner wall of the U is' ported, and the bulb is fused to the outer wall to form the seal 34, as is described 1n my co-pendin application, Serial Number 269,440, filed pril 12, 1828. A getter 36 is contained in the chamber between the walls of the U. The bulb is evacuated through a tubulation 37 in the bulb 6.

In use the plate would be cooled by 1mmersion in water of other fluid as is customary in devices of this type. The tubular shield, with its openings ex-ternal to the device, permits the circulation of fluid therethrough to carry away its excess heat. The particular conditions to be met would determine whether the fluid used would be water, oil or air, and whether thermo-siphon or forced circulation be used.

Modifications of this structure are shown in Figures 5, 6 and 7. Figure 5 shows the grid and shield as interwound spirals. Figgrid wires 17 and shield 21 are distinguished prime marks from the similar parts in the figures showing the preferred embodiment.

In all of the modifications shown, the operation is the same. The shield is charged ositively with respect to the cathode, the fbrm of its electrostatic field being determined primarily by the ed es presented toward cathode and anode. T e field from the outer edges shields the grid from electrostatic capacity effects to the anode. The field from the inner edges largely neutralizes the space charge of the electron stream.

I claim:

1. An electrical discharge device comprising a cathode, an anode, a grid, and a hollow shield electrode between the anode and cathode adapted for the circulation of afluid therethrough.

2. An electrical discharge device comprising a cathode, an anode, a grid, and a tubular shield electrode be ween the anode and cathode adapted for the circulation of a fluid therethrough and the position of which with respect to the anode and cathode is coincident with that of the grid.

3. An electrical discharge apparatus comprising an evacuated chamber; a cathode, an anode and a grid disposed within said chamber, and a tubular shield electrode interposed between adjacent elements of said grid and opening, externally of said chamber, to permit the circulation of a fluid through said shield.

4. A thermionic relay comprising a cathode, an anode, a grid, and a shield electrode comprising a flattened tube interposed between adjacent elements of said grid and mounted to present its smaller dimension to said cathode and anode.

5. An electron tube comprising an anode, a cathode, a grid and a reticulate shielding electrode between the anode and cathode, the grid lying entirely within the boundaries de fined by the shielding electrode between the reticulations thereof, the shielding electrode extending beyond the grid both in the direction of the cathode and in the direction of the anode.

6. An electron tube comprising an anode, a cathode, and between the anode and the cathode a grid and a shielding electrode, the grid and shielding electrode being correspondingly positioned with respect to the anode and cathode having their central axes coincident and having the same mean radii, the grid lying within the confines of the shielding electrode, the cross-sectional dimension of the grid being less than that of the shielding electrode whereby portions of the shielding electrode project beyond the grid toward both the cathode and the anode.

7. An electron tube comprising an anode and a cathode and a grid interposed between the anode and cathode, a shielding electrode between the anode and cathode in the same relative position with respect to the anode and cathode as the grid and having substantially the same contour as the grid, the shielding electrode and the grid being out of contact with each other, the grid lying substantially within the confines of the shielding electrode, and the shielding electrode projecting beyond the grid on one side toward the anode and on the other side toward the cathode.

8. An electron tube having an anode and a cathode and a grid interposed between the anode and cathode, a shielding electrode between the anode and cathode in the same relative position with respect to the anode and cathode as the grid and having substantially the same contour as the rid, the shielding electrode and the grid belng out of contact with each other, the grid lying substantially within the confines of the shielding electrode, and the shielding electrode projecting beyond the grid on one side toward the anode and on the other side toward the cathode, said shielding electrode being hollow and being of greater cross-sectional dimensions than the grid, and connections to the shielding electrode through which cooling fluid may flow into and out of the shielding electrode.

9. An electrical discharge device comprising an anode, a cathode, a reticulated grid disposed between the anode and the cathode, and a shielding electrode positioned coincident with the grid between the anode and the cathode, the shielding electrode projecting beyond the inner face of the grid closer to the cathode than the id and projecting beyond the outer face 0 the grid closer to to the anode.

10. An electrical discharge device comprising grid disposed between the anode and the oathode, and a reticulated fourth electrode positioned coincident with the grid between the anode and the cathode, the said fourth electrode having the reticulated portions thereof positioned between the corresponding portions of the gridand being out of contact therewith, the fourth electrode being of greater transverse Width than the grid and prO ecting beyond one face of the grid closer to the anode and beyond the other face of the grid closer to the cathode.

In testimony whereof, I have hereunto m hand.

FREDERICK S. MCCULLOUGH.

an anode, a cathode, a reticulated 

